Carry out studies to understand the role of breast milk in supplying nutrition to both full-term and premature infants, and the physiological basis of changes in milk composition which occur during the course of human lactation. Specifically: provide a comprehensive set of longitudinal data on the composition of breast milk from a homogenous reference sample of lactating women; and determine the effect of certain maternal conditions on the concentration of themajor constituents of milk and cholostrum.